Enzyme production by lactobacilli and the potential link with infective endocarditis

H.J. OAKEY, D.W.S. HARTY AND K.W. KNOX. 1995. Fifty‐six strains of lactobacilli were examined for the production of glycosidases and proteases (arylamidases) that could be associated with the ability to grow in vivo and/or be a factor in the pathogenesis of endocarditis. The strains were from seven species, with an emphasis on Lactobacillus rhamnosus and Lact. paracasei subsp. paracasei, both of which have been associated with endocarditis and provided 12 of the 13 strains isolated from cases of the disease. Other species were Lact. acidophilus, Lact. plantarum, Lact. salivarius, Lact. fermentum and Lact. oris. Commonly expressed glycosidase activities were α‐D‐galactosidase and β‐N‐acetyl‐D‐glucosaminidase followed by β‐D‐glucosidase and α‐L‐fucosidase. The combined production of β‐N‐acetyl‐D‐glucosaminidase and α‐D‐galactosidase was a feature of the endocarditis isolates. In contrast, β‐D‐galactosidase was produced by very few of the strains within species implicated in endocarditis but most of the strains of Lact. salivarius, Lact. fermentum and Lact. oris. The most commonly produced arylamidases active against substrates employed for testing human blood clotting cascade were activated protein C(Ca)‐like, activated factor X(Xa)‐like and Hageman factor‐like followed by kallikrein‐like and chymotrypsin‐like enzymes. Kallikrein‐like enzyme activity was shown more frequently by strains from species commonly isolated from cases of endocarditis (Lact. rhamnosus and Lact. paracasei subsp. paracasei) than from other oral species (Lact. plantarum, Lact. salivarius, Lact. fermentum and Lact. oris). The data indicate that some lactobacilli can produce enzymes that would enable the breakdown of human glycoproteins and the synthesis and lysis of human fibrin clots, characteristics which aid the colonization and survival of bacteria infecting an endocarditis vegetation.